Author: Frederic Massart
MDL-30070 message: Web Services for contact list
http://git.moodle.org/gw?p=moodle.git;a=commit;h=d6731600c89157d8e9ac46be93bf84fdc818ec56
http://github.com/moodle/moodle/commit/d6731600c89157d8e9ac46be93bf84fdc818ec56
+ 2.5 en [querystringcannotbeempty,core_error]